$re = '/(?:[-_]?[0-9]+x[0-9]+)+/';
$str = 'http://url.com/0304-parapente-lagoon-Reunion-96x64.jpg
http://url.com/0304-parapente-lagoon-Reunion-960x640.jpg
http://url.com/0304-parapente-lagoon-Reunion-1500x1000.jpg
http://url.com/0304-parapente-lagoon-Reunion-1280x840-960x640.jpg
http://url.com/0304-parapente-lagoon-Reunion.jpg
http://url.com/520963918_960x540.jpg';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php